This invention relates to an expansion bolt unit, more particularly to an expansion bolt unit which can be used repeatedly.
The improvement of this invention is directed to a conventional expansion bolt unit for architectural uses. Referring to FIG. 1, such a unit 10 includes an expansion tube 11 having a plurality of jaw segments 12 at an end portion thereof which are defined by axially extending slits 13, and a bolt member 14 having a frusto-conical section 15 and an externally threaded cylindrical section 16. A washer 17 and a retaining ring 18 are sleeved on the bolt member 14. A nut 19 is engaged with the cylindrical section 16.
In use, the frusto-conical section 15 of the bolt member 14 expands the jaw segments 12 as a result of the outward pull on the bolt member 14, thereby anchoring the unit 10 in a concrete structure such as the foundation of a house. However, it is difficult to remove the unit 10 from the masonry, concrete, or other rigid structure after use. Because this situation renders it impossible to repeatedly use the unit 10, manufacturers tend to make such a unit from inexpensive metals, such as copper and copper alloy, thereby weakening the unit.